In Vim is there more than one way to leave insert mode?

Question

There are several commands that do something and then enter insert mode. Are there also commands that leave insert mode and do things?

For example, I frequently do this...

control[ : w return

Before I create a mapping, is there already Vim command that does that?

Answer 1

In addition to Esc (which is identical to ^[), ^C also exits insert mode.

Answer 2

The only one I can think of is c-o, which lets you run one command in normal mode then drops you back into insert mode.

For example, a<c-o>~b would result in Ab.